The present invention relates generally to electromagnetic contactors, and more particularly to an electro-mechanical reversing contactor having a common base and having a mechanical interlock.
Reversing contactors are known in the art and generally are comprised of two separate contactors, each having a powerhead that includes at least a pair of stationary contacts and a pair of movable contacts. The movable contacts are mounted on a movable carrier that is typically attached to an armature, all in the powerhead. Each powerhead is mounted in its own separate base housing that typically includes an electromagnet, that when energized, magnetically forces the armature to change positions and, typically, close the contacts. To form a reversing contactor, two such individual contactors are mounted side-by-side with some form of interlock therebetween.
Reversing contactors are typically used to connect motor windings of either a two-speed or a reversible motor directly to a power supply. Consequently, some means must be provided to preclude simultaneously closing the individual contactors. It is therefore a requirement that such contactors be positively interlocked to prevent the completion of a circuit through more than one relay at any given instant.
Various mechanical interlock devices have been devised to perform this function, and although such devices have generally served their purpose, no single device has proven entirely satisfactory from a cost, assembly, and operational standpoint. For example, some prior interlock devices are bulky in size utilizing a large number of parts which results in a complicated mechanism to perform the interlocking function. Such designs are generally costly to manufacture and are susceptible to failure. Further, some of these devices have outwardly exposed components, which may be easily defeated, invite tampering, or which may present a possible electrical hazard.
More recently, mechanical interlocking devices having fewer parts and being smaller in size have been developed which tend to minimize some of the aforementioned problems. However, these devices have not entirely satisfied the need for improvement in that many of these devices use small parts that make it difficult to assemble and/or repair. That is, these newer devices tend to require more care and assembly time to ensure that both contactors cannot be simultaneously energized at any given time. Some of the newer devices have interlocking elements which must be bent or must pivot in a comprehensive manner, and consequently, they tend to become less reliable with age and use since the interlocking element may fail to rebound to the neutral position and can remain in a blocking position at all times.
Mechanically linking or mounting two contactors is yet another labor intensive process and requires additional hardware. With the ever increasing cost of labor and the demand to reduce cost and materials, it would be advantageous to have a single, common base to receive two powerheads, thus eliminating two separate bases mounted to a common mounting plate. In such an arrangement, additional savings is achieved by the use of a single, common circuit board for both powerheads. It would be additionally advantageous to have such a common base that includes structure to provide an interlocking function between the two powerheads and uses minimal components and is relatively easy to assemble.